Summary of Significant Accounting Principles - Prior Period Adjustment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss	$ (2,293)	$ (808)	$ (4,101)	$ (2,016)
Contract revenues	137,420	140,301		269,924
Costs of contract revenues	122,023	123,355		238,267
Selling, general and administrative expenses	17,528	16,899		32,437
Income tax expense	$ (1,624)	$ (502)		$ (1,252)